By default, your site's main navigation collapses to a drop-down menu on mobile devices. However, for your site's homepage in desktop view, you can choose to show the full navigation if the number of links is less than or equal to a certain threshold.
The default threshold is 7; set this number to 1 if you prefer to always collapse the navigation on the homepage, or set it to a high number (say, 100) if you prefer to never collapse it on the homepage.
To change the threshold and make your menu fully collapsed, follow these steps:
1. Select the Settings gear icon from the gray navigation bar and hover over the Extras tab under the Settings header.
2. Select Mobile from the drop-down menu. Set the Home page nav collapse threshold to 1.
3. Select the green Publish button to make the change live to your site.